The present invention relates to a radiation tomography system and a tomography method. More particularly, the present invention is concerned with a radiation tomography system and a tomography method that display a control value with which an exposure of X-rays radiated from an X-ray source is controlled.
As a modality for producing tomographic images, for example, X-ray computed tomography (CT) systems are known. The X-ray CT system irradiates, for example, X-rays as a radiation, detects X-rays having passed through a subject, and produces tomographic images through calculation.
The X-ray CT system includes a scanner gantry composed of an X-ray tube and a detector array opposed to the X-ray tube with a subject between them. The detector array detects X-rays irradiated from the X-ray tube to the subject. The X-ray CT system moves the scanner gantry while rotating it about the subject, and thus scans the subject in a direction parallel to the direction of a body axis linking the subject's head and the subject's tiptoe. Consequently, a plurality of views of projection data is produced. The X-ray CT system recomposes acquired projection data to produce tomographic images of a predetermined slice thickness representing the subject.
A facility is known for automatically controlling a control value with which an exposure of X-rays radiated from the X-ray tube is controlled, for example, a value of a tube current to be fed to the X-ray tube according to a scanned position in a subject. Known as an X-ray CT system including the facility is a system that calculates tube current values, which are associated with regions whose X-ray absorption doses are different from one another, for each turn, and displays the calculated tube current values in the form of a text or a graph (refer to, for example, Patent Document 1).
However, according to Patent Document 1, the calculated tube current values are displayed as discrete values calculated for each turn of the scanner gantry in association with positions in the body-axis direction. Consequently, a user cannot check the tube current values to be attained during each turn.
Moreover, when a helical scan is performed, that is, when reconstructed images are inconsistent with turns, or when a turn out of turns made by the scanner gantry during which certain image data has been acquired is hardly identified due to adoption of a multi-slice imaging technique, it is hard to identify a tube current value used to reconstruct an image.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2002-177261